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At least 19 recordsLinked to original sources
PubMed2002

The first report on the occurrence of twins in a freshwater crayfish, Pacifastacus leniusculus (Decapoda, Astacoidea).

Twin stage 1 juveniles from the signal crayfish, Pacifastacus leniusculus, were observed in this study. No such observations have been found in the literature. The twins consist of two stage 1 juveniles that are fused at the head. Each juvenile has a separate abdomen and thorax and has the appropriate number of appendages and a telson, all characteristic of a normal stage 1 juvenile.

Animals↗
PubMed2003

Two genetic variants of the crustacean hyperglycemic hormone (CHH) from the Australian crayfish, Cherax destructor: detection of chiral isoforms due to posttranslational modification.

From sinus glands of the Australian crayfish Cherax destructor, two genetic variants of the crustacean hyperglycemic hormone (CHH) were isolated by HPLC and fully characterized by mass spectrometry and Edman sequencing. Both CHH A (8350.38 Da) and CHH B (8370.34 Da) consist of 72 amino acid residues, with pyroGlu as N-terminus and an amidated (Val-NH2) C-terminus. They differ in 14 residues (81% identity). Both sequences are significantly different from those of the hitherto known three CHHs of Astacoidea species (Northern hemisphere crayfish), which among themselves are extremely conserved. This may reflect the long, separate evolution of the Astacoidea lineage and the Parastacoidea (Southern hemisphere crayfish) lineage, to which Cherax belongs. CHH A and CHH B genes are expressed at comparable levels, as indicated by the similar amounts of mature peptides in the sinus gland. In addition to each of the major peptides, which share the identical N-terminal tripeptide pyroGlu-Val-L-Phe, one chiral isoform containing pyroGlu-Val-D-Phe was identified. Compared to the main peptides, the amounts of the D-isoforms are lower, but significant, amounting to 30-40% of L-isoforms. These results demonstrate that two genes can give rise to a total of four different peptides in the secretory terminals of the sinus gland. All peptides gave a highly significant hyperglycemic in vivo response in C. destructor.

Amino Acid Sequence↗
PubMed2000

The monophyletic origin of freshwater crayfish estimated from nuclear and mitochondrial DNA sequences.

Despite their widespread use as model organisms, the phylogenetic status of the around 520 species of freshwater crayfish is still in doubt. One hypothesis suggests two distinct origins of freshwater crayfish as indicated by their geographical distribution, with two centres of origin near the two present centres of diversity; one in south-eastern United States and the other in Victoria, Australia. An alternative theory proposes a single (monophyletic) origin of freshwater crayfish. Here we use over 3000 nucleotides from three different gene regions in estimating phylogenetic relationships among freshwater crayfish and related Crustacea. We show clear evidence for monophyly of freshwater crayfish and for the sister-group relationship between crayfish and clawed lobsters. Monophyly of the superfamilies Astacoidea and Parastacoidea is also supported. However, the monophyly of the family Cambaridae is questioned with the genus Cambaroides being associated with the Astacidae.

Animals↗
PubMed2006

Crustacean hyperglycemic and vitellogenesis-inhibiting hormones in the lobster Homarus gammarus.

Crustacean hyperglycemic hormone (CHH) and vitellogenesis-inhibiting hormone (VIH), produced by the X organ-sinus gland neurosecretory complex, belong to a peptide group referred to as the CHH family, which is widely distributed in arthropods. In this study, genetic variants and post-translationally modified isoforms of CHH and VIH were characterized in the European lobster Homarus gammarus. With the use of RP-HPLC and ELISA with specific antibodies that discriminate between stereoisomers of CHH and VIH, two groups of CHH-immunoreactive peaks were characterized from HPLC fractions of sinus gland extract (CHH A and CHH B); each group contained two variants (CHH and D-Phe3CHH). In the same way, two VIH-immunoreactive peaks (VIH and D-Trp4VIH) were demonstrated in HPLC fractions from sinus gland extract. The masses of these different neuropeptides were determined by FT-ICR MS: CHH A and CHH B spectra exhibited monoisotopic ions at 8557.05 Da and 8527.04 Da, respectively, and both VIH isomers displayed an m/z value of 9129.19 Da. Two full-length cDNAs encoding preprohomones of CHH A and CHH B and only one cDNA for VIH precursor were cloned and sequenced from X organ RNA. Comparison of CHH sequences between European lobster and other Astacoidea suggests that the most hydrophobic form appeared first during crustacean evolution.

Amino Acid Sequence↗
PubMed1996

Neuroanatomy of a crayfish thoracic ganglion: sensory and motor roots of the walking-leg nerves and possible homologies with insects.

The internal organization of the third and fourth thoracic ganglia of the crayfish, Pacifastacus leniusculus, was studied in serial sections stained with osmium ethyl gallate. The aims were 1) to provide an anatomical framework for studies of sensorimotor integration in the walking system and 2) to explore possible homologies with abdominal ganglia in crayfish and with the thoracic ganglia of insects. Crayfish thoracic ganglia show several intersegmental homologies with the unfused ganglia of the abdominal nervous system: 1) Longitudinal tracts and dorsal commissures are arranged similarly, allowing use of the same nomenclature. 2) Paired lateral neuropils are located dorsolaterally and contain many large neurites including those of leg motor neurons and of nonspiking, proprioceptive afferents from the basal limb joints. They resemble the lateral neuropils of abdominal ganglia. 3) Neuropil lying more ventrally is fine textured and receives projections from other leg afferents. This ventral neuropil resembles the "horseshoe neuropil" of abdominal ganglia. The functional implications of this organization are discussed. Compared to the abdominal ganglia, however, thoracic ganglia also show specific intersegmental differences: 1) They have more ventral commissures; 2) the ventral neuropil undergoes a large bilateral extension; 3) distinct anteromedial regions of the ventral neuropil receive specific afferent projections; and 4) recognizable dorsoventral "T-tracts" occur. Moreover, these "thoracic" features show a striking resemblance to structures found in thoracic ganglia of orthopteran insects. These correspondences provide further indications that the neuropil of segmental ganglia may be organized in homologous ways in crustaceans and in insects.

Animals↗
PubMed1996

Structural features of crayfish phasic and tonic neuromuscular terminals.

We examined the fine structure of terminals of the phasic and tonic excitatory axon to the crayfish limb extensor muscle. The phasic terminals are known to release 50-100 times more transmitter for a small length of terminal for a single impulse. Phasic terminals labeled with horseradish peroxidase (HRP) were relatively thin and contained a single unbranched mitochondrion; tonic terminals were much thicker, and their varicosities contained several multibranched mitochondria. Tonic terminals devoted a larger proportion of their total volume to mitochondria. The percentage volume of clear synaptic vesicles was slightly higher in phasic axon terminals, but as the tonic axon terminals were fivefold larger in volume, the total synaptic volume is much greater in tonic than phasic terminals. The number of synapses per length of terminal, and the total number of active zones per length of terminal, were greater for tonic terminals, and individual synapses were, on average, slightly larger in surface contact area for tonic terminals. In contrast, individual active zones were, on average, longer in phasic synapses. A higher proportion (50%) of phasic synapses had multiple active zones than was the case for tonic synapses (16%), and pairs of closely spaced active zones were more frequently found on phasic synapses. These findings clearly rule out synapse and active zone number as a factor contributing to higher transmitter output, but suggest that active zone size and synaptic complexity, as evidenced by multiple closely spaced active zones in a single synapse, are likely to play a causal role in the greater transmitter release of the phasic terminal. Even synapse complexity would not be enough to account fully for the large difference in terminal transmitter output, and additional factors may include electrical and biochemical differences.

Animals↗
PubMed1996

Quantal release at visualized terminals of a crayfish motor axon: intraterminal and regional differences.

Synaptic transmission was measured at visualized terminal varicosities of the motor axon providing the sole excitatory innervation of the "opener" muscle in walking legs of crayfish (Procambarus clarkii Girard). Two questions were addressed: 1) How uniform is quantal emission at different locations along terminals innervating a single muscle fiber, and 2) can differences in quantal emission account for the different excitatory postsynaptic potential (EPSP) amplitudes generated by terminals localized in defined regions of the muscle? Extracellular "macropatch" electrodes were placed over individual varicosities, viewed after brief exposure to a fluorescent dye, and synaptic currents were recorded to determine quantal content of transmission. Along terminals supplying a single muscle fiber, nonuniform release was found: Varicosities closer to the point of origin of the terminal branch released more transmitter than those located more distally. Quantal content was higher for varicosities of the muscle's proximal region (where large EPSPs occur) than for varicosities of the central region (where small EPSPs occur). The probability of transmitter release per synapse is estimated to be greater for the proximal varicosities. At low frequencies of stimulation, quantal content per muscle fiber is two to four times larger in the proximal region. Taken in conjunction with a twofold higher mean input resistance for the proximal muscle fibers, the difference in quantal content can account for a four- to eightfold difference in EPSP amplitude. The observed mean EPSP amplitude is at least eight times larger in the proximal region. We discuss factors contributing to differences in EPSP amplitudes.

Animals↗
PubMed1997

Distribution of GABAergic premotor nonspiking local interneurones in the terminal abdominal ganglion of the crayfish.

The inhibitory neurotransmitter of premotor nonspiking local interneurones in the crayfish terminal abdominal ganglion was investigated physiologically and immunocytochemically. Depolarization of a nonspiking interneurone evoked a hyperpolarization in a uropod motor neurone. The amplitude of hyperpolarization in the motor neurone was gradually decreased under low-calcium/high-magnesium saline. Local pressure injection of gamma-aminobutyric acid (GABA) into the neuropil caused a similar hyperpolarization of the motor neurone. These physiological studies suggested a GABAergic inhibitory interaction between nonspiking interneurones and the motor neurones. Premotor nonspiking interneurones are classified into two subgroups ofposterolateral (PL) and anterolateral (AL) interneurones, and AL interneurones are further divided into three subtypes. A combination of intracellular staining from nonspiking local interneurones with Lucifer yellow and immunocytochemical staining with an antiserum directed against GABA revealed that all the PL interneurones sampled in this study showed GABA-like immunoreactivity. A population of cell bodies (n = 6-11) with a small diameter (15-30 microm) packed together forming a cluster showed GABA-like immunoreactivity, and the cell bodies of most PL interneurones were found in this cluster. To compare the number and the pattern of main branches of PL interneurones, cells were classified into three identifiable sets of interneurones, called PL-1, PL-2, and PL-3. By contrast, about one-half of AL interneurones, especially the third subtype of AL interneurones, which have cell bodies located ventrolaterally in the ganglion, did not show GABA-like immunoreactivity. Furthermore, the position of cell bodies of GABA-immunoreactive AL interneurones was scattered compared to that of PL interneurones.

Abdomen↗
PubMed1998

Quantitative analyses of anatomical and electrotonic structures of crayfish nonspiking interneurons by three-dimensional morphometry.

The three-dimensional structure of premotor nonspiking interneurons in the terminal abdominal ganglion of crayfish have been studied quantitatively by using a confocal laser-scanning microscope. Their passive membrane properties have also been studied electrophysiologically to analyze their electrotonic structure. In either one of the two major morphological types, anterolateral (AL) and posterolateral (PL), that are characterized by different locations of cell bodies in the ganglion, the monopolar cell body is connected with a fine primary process to a thick main segment projecting numerous fine secondary processes. These two types of cells share a common dendritic field in the neuropil, showing similar anatomical characteristics of dendrites. Electrotonic analyses based on the present anatomical and physiological measurements have revealed that the steady-state voltage-attenuation factors for the secondary processes were not statistically different between the AL- and PL-type cells. Comparison between the premotor nonspiking interneurons and an identified sensory nonspiking interneuron, which was studied previously, has revealed that voltage attenuation over secondary processes in both the centripetal and the centrifugal directions was significantly greater in the sensory than in the premotor interneurons, although the anatomical length of each secondary process from its terminal to the main segment was not different between them. Differences in the electrotonic structure between sensory and premotor nonspiking interneurons indicate their different modes of synaptic integration in the control of postsynaptic nerve cells.

Animals↗
PubMed1998

Heat-shock proteins in axoplasm: high constitutive levels and transfer of inducible isoforms from glia.

To characterize heat-shock proteins (HSPs) of the 70-kDa family in the crayfish medial giant axon (MGA), we analyzed axoplasmic proteins separately from proteins of the glial sheath. Several different molecular weight isoforms of constitutive HSP 70s that were detected on immunoblots were approximately 1-3% of the total protein in the axoplasm of MGAs. To investigate inducible HSPs, MGAs were heat shocked in vitro or in vivo, then the axon was bathed in radiolabeled amino acid for 4 hours. After either heat-shock treatment, protein synthesis in the glial sheath was decreased compared with that of control axons, and newly synthesized proteins of 72 kDa, 84 kDa, and 87 kDa appeared in both the axoplasm and the sheath. Because these radiolabeled proteins were present in MGAs only after heat-shock treatments, we interpreted the newly synthesized proteins of 72 kDa, 84 kDa, and 87 kDa to be inducible HSPs. Furthermore, the 72-kDa radiolabeled band in heat-shocked axoplasm and glial sheath samples comigrated with a band possessing HSP 70 immunoreactivity. The amount of heat-induced proteins in axoplasm samples was greater after a 2-hour heat shock than after a 1-hour heat shock. These data indicate that MGA axoplasm contains relatively high levels of constitutive HSP 70s and that, after heat shock, MGA axoplasm obtains inducible HSPs of 72 kDa, 84 kDa, and 87 kDa from the glial sheath. These constitutive and inducible HSPs may help MGAs maintain essential structures and functions following acute heat shock.

Action Potentials↗
PubMed2000

Functional organization of crayfish abdominal ganglia. III. Swimmeret motor neurons.

Swimmerets are limbs on several segments of the crayfish abdomen that are used for forward swimming and other behaviors. We present evidence that the functional modules demonstrated previously in physiological experiments are reflected in the morphological disposition of swimmeret motor neurons. The single nerve that innervates each swimmeret divides into two branches that separately contain the axons of power-stroke and return-stroke motor neurons. We used Co(++) or biocytin to backfill the entire pool of neurons that innervated a swimmeret, or functional subsets whose axons occurred in particular branches. Each filled cell body extended a single neurite that projected first to the Lateral Neuropil (LN), and there branched to form dendritic structures and its axon. All the motor neurons that innervated one swimmeret had cell bodies located in the ganglion from which their axons emerged, and the cell bodies of all but two of these neurons were located ipsilateral to their swimmeret. Counts of cell bodies filled from selected peripheral branches revealed about 35 power-stroke motor neurons and 35 return-stroke motor neurons. The cell bodies of these two types were segregated into different clusters within the ganglion, but both types sent their neurites into the ipsilateral LN and had their principle branches in this neuropil. We saw no significant differences in the numbers or distributions of these motor neurons in ganglia A2 through A5. These anatomical features are consistent with the physiological evidence that each swimmeret is controlled by its own neural module, which drives the alternating bursts of impulses in power-stroke and return-stroke motor neurons. We propose that the LN is the site of the synaptic circuit that generates this pattern.

Abdomen↗
PubMed2000

Distribution of ryanodine receptor Ca(2+) channels in insect photoreceptor cells.

Physiological studies have provided evidence for the existence of ryanodine receptor (RyR) Ca(2+) channels in compound eyes of insects. The present study identifies and localizes RyR in insect photoreceptors by use of an affinity-purified antibody against lobster muscle RyR. Western blotting and indirect immunofluorescence staining confirm cross-reactivity of the antibody with insect muscle RyR. In both honeybee and fly eyes, the antibody identifies a single protein that comigrates with muscle RyR on sodium dodecylsulfate (SDS) polyacrylamide gels demonstrating that RyR is present in this tissue. By confocal immunofluorescence microscopy on honeybee eyes, RyR is detected within the photoreceptors and shows a nonhomogeneous distribution over the endoplasmic reticulum (ER). Double labeling studies have demonstrated further that RyR is localized at distinct ER elements close to the light-sensitive microvilli and juxtaposed to adherens junctions. RyR has also been observed within the remaining soma of honeybee photoreceptors, being concentrated on ER cisternae close to mitochondria and the nonreceptive plasma membrane. For comparative purposes, the distribution of RyR has also been assayed in compound eyes of flies. In both Calliphora and Drosophila photoreceptors, the anti-RyR antibody provides punctate labeling throughout the cell body. The submicrovillar ER cisternae associated with the base of the microvilli, however, are only lightly labeled for RyR. These results suggest that RyR is involved with Ca(2+) regulation in the nonreceptive cell area of both fly and honeybee photoreceptors, but that it may contribute to Ca(2+) regulation close to the phototransduction compartment only in the latter cell.

Animals↗
PubMed2000

Heteromorphic antennules protect the olfactory midbrain from atrophy following chronic antennular ablation in freshwater crayfish.

Posthatch larval crayfish (Procambarus clarkii) were unilaterally antennulectomized and maintained in the laboratory for a 6-month period, during which time all regenerating antennular stumps were periodically excised. In another group of animals at a similar developmental stage a heteromorphic antennule was induced on the side of the head ipsilateral to the chronically sectioned normal antennule. After 6 months, all experimental animals were sacrificed and their brains were fixed and sectioned. Computer-aided quantitative measurements were obtained for the volumes of the olfactory lobes on both the experimental and control sides of the brains of both groups of crayfish. In the brains of the crayfish group in which only chronic antennualectomy had been performed, the olfactory lobe ipsilateral to the lesion was reduced in volume by about 80% compared to the olfactory lobe on the control side. In animals in which the normal antennule had been chronically ablated, but which possessed a heteromorphic antennule on the same side, the olfactory lobe on the lesioned side differed in volume from the control side by a mean value of only 28%. We conclude that afferent fibers from a heteromorphic antennule ipsilateral to a chronically lesioned normal antennule can assume some of the central trophic functions of the afferents from the normal antennule; thus, the presence of a heteromorphic antennule offers some measure of protection from the dystrophic effects of chronic ablation of the normal antennule during development and growth in crayfish.

Animals↗
PubMed2000

Serotonergic regulation of blood glucose levels in the crayfish, Procambarus clarkii: site of action and receptor characterization.

The present study investigated the site of action of 5-hydroxytryptamine (5-HT) and pharmacologically characterized the receptors involved in regulating blood glucose levels in the crayfish, Procambarus clarkii. Injection of 5-HT into intact animals increased glucose levels in a dose-dependent manner. In contrast, 5-HT failed to elicit a hyperglycemic response in eyestalk-ablated animals. Effects of several 5-HT receptor agonists and antagonists were examined. 5-CT, oxymetazoline (both 5-HT(1) receptor agonists) and alpha-methyl-5-HT (a 5-HT(2) receptor agonist), but not 1-phenylbiguanide, m-CPBG (both 5-HT(3) receptor agonists), or RS 67333 (a 5-HT(4) receptor agonist), induced hyperglycemic responses in a dose-dependent manner. In addition, 8-OH-DPAT (a 5-HT(1A) receptor agonist), L-694,247 (a 5-HT(1B/1D) receptor agonist), and DOI (a 5-HT(2A) receptor agonist) were effective in significantly increasing the glucose levels, whereas both BW 723C86 (a 5-HT(2B) receptor agonist) and m-CPP (a 5-HT(2C) receptor agonist) were ineffective. Finally, ketanserin (a 5-HT(2A) receptor antagonist), but not p-MPPF (a 5-HT(1A) receptor antagonist), GR 55562 (a 5-HT(1B/1D) receptor antagonist), SB 206553 (a 5-HT(2B/2C) receptor antagonist), or tropisetron (a 5-HT(3) receptor antagonist), was able to block 5-HT-induced hyperglycemia. The combined results support the hypothesis that 5-HT exerts its hyperglycemic effect by enhancing the release of hyperglycemic factor(s) from the eyestalks, and suggest that 5 HT-induced hyperglycemia is mediated by 5-HT(1)- and 5-HT(2)-like receptors.

Animals↗
PubMed1998

Activity of phasic motor neurons partially transforms the neuronal and muscle phenotype to a tonic-like state.

We present a model preparation, the crayfish, to investigate chronic stimulation effects in muscle fiber type and neuronal conversion from fast to slow. The results show a presynaptic alteration in transmitter release after 1 week of stimulation at 5 Hz for a 2-h daily regime. With the same stimulation paradigm, the muscle proteins displayed on a polyacrylamide gel only start to show changes after 3 weeks. The original phasic motoneurons within 1 week display an enhanced ability to resist synaptic depression, as do tonic motoneurons. The results show that identified phasic motoneurons and muscle fibers in the crayfish can be transformed to a toniclike state, and that the nerve terminals convert prior to the muscle fibers. Electrophysiological clinical measures indicating a change in transmitter release properties may not necessarily mean that the muscle fibers have fully adapted for long-lasting effects. This preparation allows stimulation conditions to be examined with ease.

Action Potentials↗
PubMed1996

Structure of allotransplanted ganglia and regenerated neuromuscular connections in crayfish.

In adult crayfish, Procambarus clarkii, motoneurons to a denervated abdominal superficial flexor muscle regenerate long-lasting and highly specific synaptic connections as seen from recordings of excitatory postsynaptic potentials, even when they arise from the ganglion of another crayfish. To confirm the morphological origins of these physiological connections we examined the fine structure of the allotransplanted tissue that consisted of the third abdominal ganglion and the nerve to the superficial flexor muscle (the fourth ganglion and the connecting ventral nerve cord were also included). Although there is considerable degeneration, the allotransplanted ganglia display intact areas of axon tracts, neuropil, and somata. Thus in both short (6-8 weeks) and long (24-30 weeks) term transplants approximately 20 healthy somata are present and this is more than the five axons regenerated to the host muscle. The principal neurite and dendrites of these somata receive both excitatory and inhibitory synaptic inputs, and these types of synaptic contacts also occur among the dendritic profiles of the neuropil. Axon tracts in the allotransplanted ganglia and ventral nerve cord consist largely of small diameter axons; most of the large axons including the medial and lateral giant axons are lost. The transplanted ganglia have many blood vessels and blood lacunae ensuring long-term survival. The transplanted superficial flexor nerve regenerates from the ventral to the dorsal surface of the muscle where it has five axons, each consisting of many profiles rather than a single profile. This indicates sprouting of the individual axons and accounts for the enlarged size of the regenerated nerve. The regenerated axons give rise to normal-looking synaptic terminals with well-defined synaptic contacts and presynaptic dense bars or active zones. Some of these synaptic terminals lie in close proximity to degenerating terminals, suggesting that they may inhabit old sites and in this way ensure target specificity. The presence of intact somata, neuropil, and axon tracts are factors that would contribute to the spontaneous firing of the transplanted motoneurons.

Abdomen↗
PubMed1998

Microinjection of mRNA encoding rat synapsin Ia alters synaptic physiology in identified motoneurons of the crayfish, Procambarus clarkii.

Studies of identified neurons have made important contributions to our understanding of cellular neurophysiology. We have developed a technique for modifying gene expression in identified motoneurons of the crayfish Procambarus clarkii in the isolated nervous system as well as in the intact animal through the injection of exogenously synthesized RNAs. mRNA suitable for injection was transcribed in vitro from cDNA templates cloned into a plasmid, pSEM. Initially, mRNAs encoding green fluorescent protein (GFP) and beta-galactosidase were injected into the soma of the motor giant neuron (MoG) to determine whether these mRNAs could be successfully translated into protein. Both proteins were expressed. Measurements of GFP fluorescence increase indicated that GFP mRNA was stable and translated into protein for at least 3 days postinjection. We then examined the effects of expression of GFP, AASP-168 (an endogenous crayfish axonal protein), and rat synapsin Ia on MoG synaptic physiology. The mRNA injection procedure did not appear to directly influence synaptic physiology based on the results of the AASP-168 and GFP injections. Injection of mRNA encoding rat synapsin Ia resulted in a significant increase in peak excitatory postsynaptic potential (EPSP) amplitude during repetitive stimulation. These data are consistent with previous studies that have shown that synapsin deficiency reduces synaptic vesicle numbers. The translation of mRNAs with diverse functions and species of origin suggests that this approach will prove useful for studying the function of a wide variety of endogenous and exogenous genes in identified neurons.

Animals↗